Charles's Law Calculator

Charles's Law describes the relationship between the volume and temperature of a gas when pressure is held constant. It tells us that volume and absolute temperature are directly proportional: double the temperature and the volume doubles; halve the temperature and the volume halves. The law was established by Jacques Charles in the late 18th century and is expressed as V1 divided by T1 equals V2 divided by T2, where V1 and T1 are the initial volume and temperature, and V2 and T2 are the final volume and temperature. Crucially, temperatures must be in kelvin for this law to work. Zero on the Celsius scale is not the true zero of heat energy; the kelvin scale starts at absolute zero, which is approximately minus 273.15 degrees Celsius. To convert, simply add 273.15 to any Celsius temperature. Everyday examples of Charles's Law include hot air balloons (hotter air expands and becomes less dense, providing lift), bread dough rising faster in a warm kitchen (carbon dioxide gas from yeast expands), and a basketball becoming slightly smaller on a cold day. This calculator lets you solve for any one of the four variables. Choose which one you want to find, enter the remaining three, and the calculator returns the result. Volume can be in any consistent unit (litres or cubic metres), as long as both volumes use the same unit.

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Temperature must be in kelvin (K = °C + 273.15). Charles's Law assumes constant pressure and ideal gas behaviour.